Vs. Reddy et al., ENERGETICS OF QUASIEQUIVALENCE - COMPUTATIONAL ANALYSIS OF PROTEIN-PROTEIN INTERACTIONS IN ICOSAHEDRAL VIRUSES, Biophysical journal, 74(1), 1998, pp. 546-558
Quaternary structure polymorphism found in quasiequivalent virus capsi
ds provides a static framework for studying the dynamics of protein in
teractions. The same protein subunits are found in different structura
l environments within these particles, and in some cases, the molecula
r switching required for the polymorphic quaternary interactions is ob
vious from high-resolution crystallographic studies. Employing atomic
resolution structures, molecular mechanics, and continuum electrostati
c methods, we have computed association energies for unique subunit in
terfaces of three icosahedral viruses, black beetle virus, southern be
an virus, and human rhinovirus 14. To quantify the chemical determinan
ts of quasiequivalence, the energetic contributions of individual resi
dues forming quasiequivalent interfaces were calculated and compared,
The potential significance of the differences in stabilities at quasie
quivalent interfaces was then explored with the combinatorial assembly
approach. The analysis shows that the unique association energies com
puted for each virus serve as a sensitive basis set that may determine
distinct intermediates and pathways of virus capsid assembly. The pat
hways for the quasiequivalent viruses displayed isoenergetic oligomers
at specific points, suggesting that these may determine the quaternar
y structure polymorphism required for the assembly of a quasiequivalen
t particle.